The value of soil

“For all things come from earth, and all things end by becoming earth.” Xenophanes, 580 B.C. You could, in reading this quote, be mistaken in thinking that the soil is a regenerating, renewable resource. Soil is formed from slowly decomposing rocks, sediment and organic matter. This process is so slow in fact that it takes 2,000 years to build 10cm of topsoil, such an unhurried rate of growth that soil should be thought of as finite, non-renewable and a resource that needs to be protected.

Healthy soils provide a variety of ecosystem services such as nutrient cycling, water regulation, flood protection, habitats for biodiversity and food production. For approximately 1 to 1.5 billion people in the world land degradation is reducing some of these services, negatively impacting their quality of life and livelihoods.

So far we haven’t been doing a very good job of protecting the soil. We overuse and cultivate unsuitable land which leads to land degradation. Soils left bare in conventional farming practices and farming on slopes accelerate soil loss and erosion. Forests and plants protect the soil but every year 13 million hectares of forest are cut down and to date an estimated 75% of the world’s primary forest has been cleared.

In 2011, an estimated 24 billion tonnes of soil were lost, which amounts to some 3.4 tonnes of soil lost per person. The United Nations Food and Agriculture Organisation estimates that one quarter of the world’s 13 billion hectares of land is degraded. In the pursuit of greater yields and profits we have compromised soil health, mining soils for nutrients, over-using fertilizers, creating over 4 billion hectares of man-made deserts and depleting over 8 billion hectares of deep organic soils.

Soils for Life, an Australian project, produced a video for 2012 Global Soil Week, which likens the world’s store of soils to money in a bank account, from which we continually withdraw without paying in.

Only more recently have we begun to explore the costs land degradation imposes on the environment and society.Soil degradation costs every person on the planet $70 each year, totalling $490 billion and this doesn’t include the indirect impacts of poor soils such as reduced water supply and declining crop yields, in turn leading to poverty, food insecurity and conflict, impacts that are only expected to worsen. In Africa two-thirds of crop land is expected to be lost by 2025. One thing is clear: it is not economically viable to carry on using and exploiting soils in the way we do today.

Recently the Economics of Land Degradation (ELD) Initiative produced a video explaining the value of soil. The video explains that degraded soils leave us vulnerable, reducing ecosystem goods and services and resilience. For example degraded soils can’t store as much carbon, contributing to climate change. But soils can also be degraded as a result of changing weather patterns.

Both videos point to sustainable land management as the answer to land degradation and declining soil resources. While acknowledged as being expensive to implement, such practices are more cost effective over the long-term. Through farming methods such as conservation tillage we can rebuild soil stores. Some studies have shown that organic matter can increase by as much as 1,800 pounds per acre per year under long-term no-till production. Sustainable land management practices could, it’s estimated, add additional crop production of 230 billion tonnes each year.

We cannot overlook soil as there is no life without it. There is hope for the future that through sustainable agricultural practices we can reverse current trends of land degradation. But we need a better understanding of the value of soils, the processes that occur in soils and the best way to protect and restore soil reserves. To end with another quote: “We know more about the movement of celestial bodies than about the soil underfoot.” Leonardo DaVinci, circa 1500s.

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This blog is run by Agriculture for Impact (A4I), an independent advocacy initiative led by Professor Sir Gordon Conway, author of the book One Billion Hungry: Can We Feed the World?

A4I aims to enable better European government support for productive, sustainable, equitable and resilient agricultural development in sub-Saharan Africa, focusing in particular on the needs of smallholder farmers.

Agriculture for Impact also convenes the Montpellier Panel, a group of European and African experts in the fields of agriculture, trade, ecology and global development.

It is based at Imperial College London and is supported through the Bill & Melinda Gates Foundation